This invention pertains to hydrogen chloride and more in particular to a method to remove impurities from anhydrous hydrogen chloride.
Hydrogen chloride is produced as a byproduct in many chemical processes. Frequently the byproduct hydrogen chloride is contaminated with organic compounds which make the hydrogen chloride unsuitable for certain applications. For example, use of anhydrous hydrogen chloride in the electronics industry for semiconductor purposes requires hydrogen chloride with a minimal amount of organic impurities. Various procedures have been previously used to reduce the level of organic compounds, for example, chlorinated compounds in hydrogen chloride with varying degrees of success. Hydrogenation utilizing platinum or palladium based catalysts to convert acetylene to ethane has been employed: however, this process is ineffective in removing saturated hydrocarbons from the hydrogen chloride. Hydrochlorination using aluminum, zinc or mercuric chloride based catalysts will convert ethylene and acetylene to chlorinated organics. Oxidation technology wherein oxygen is added to the hydrogen chloride at high temperatures to oxidize acetylene to carbon dioxide results in the so treated hydrogen chloride being contaminated with carbon dioxide which is difficult to remove by conventional distillation. The oxidation technology is also deficient in that it requires relatively large amounts of energy to achieve the relatively high temperatures required.
A process is needed to purify impure gaseous hydrogen chloride economically and rapidly without requiring high temperatures.